Antimicrobial combinations of formaldehyde substituted hydantoin, particularly 1,3-dimethylol-5,5-dimethyl hydantoin (abbreviated for convenience as DMDMH), with various selected other antimicrobial agents are desirable additives for use in a variety of personal care preparations, particularly cosmetics. Multiple usage personal care preparations, such as shampoos, skin lotions and the like, are especially prone to exposure to bacterial contamination during repeated opening of the container for product usage.
Although DMDMH is a broad spectrum antimicrobial, it is primarily active against bacteria and less active against fungi. Thus, to fully achieve broad spectrum antimicrobial activity, DMDMH is frequently combined with a second component that is particularly active against fungi. Also, the two components in combination should preferably be water soluble and achieve a greater antimicrobial effectiveness than either component used separately at equivalent concentrations.
Conventionally, the second, anti-fungal component employed is a paraben (or paraben mixture). The parabens are esters of parahydroxy benzoic acid (para acid). The parabens can only function in the water phase of a product but are not readily water soluble. Moreover, the parabens can be partially or fully inactivated by hydrogen bonders, such as highly ethoxylated compounds, e.g., polysorbates, by cellulose derivatives, proteins and the like which are frequent ingredients in personal care preparations. There is an ongoing need, therefore, for alternative antifungal components for use in combination with DMDMH.
Recent favorable experience and manufacturer response by the personal care industry has been achieved with the use of 3-iodo-2-propynyl butyl carbamate (abbreviated for convenience as IPBC), a potent fungicide but weak biocide. Consequently, a demand for combinations of DMDMH and IPBC has arisen.
Some dry powder blends of DMDMH and IPBC are disclosed by Merianos in U.S. Pat. No. 5,428,050 and No. 5,496,842 and by Rosen et al., in U.S. Pat. No. 4,844,891. However, for additive use in personal care preparations, such dry blends either must be first dissolved, usually in water before being admixed with such a preparation, or must be carefully directly added to a preparation and dissolved therein. Not only is either of such addition sequence time-consuming, but also each sequence is unpredictable and unreliable as to whether or not homogeneous dissolution and distribution will be achieved. Further, such dry blends present handling problems, such as dusting, spillage and the like.
Moreover, IPBC has a limited solubility in water of reportedly about 160-200 parts per million (0.016-0.02%). Thus, as the amount of IPBC increases in dry blends of DMDMH and IPBC, the water solubility of the blend decreases. Merianos, in U.S. Pat. No. 5,428;050 and No. 5,496,842, teaches, for example, that a high weight ratio of DMDMH to IPBC of upwards of 100:1 to 2000:1 in a DMDMH:IPBC powder blend is needed for water solubility and that at DMDMH:IPBC weight ratios below 100:1, it is difficult to uniformly distribute the iodopropynyl compound in aqueous use compositions.
A liquid composition containing predispersed DMDMH and IPBC, therefore, appears to offer the advantages of being readily admixable with aqueous or nonaqueous preparations and of achieving homogeneous distribution in the resulting finished system.
Some liquid compositions of DMDMH and IPBC are described by Merianos in U.S. Pat. No. 5,496,842,. No. 5,552,425 and No. 5,631,273 which are prepared by using the foregoing water soluble, dry blend of DMDMH and IPBC predispersed in propylene glycol or 1,3-butylene glycol. The two foregoing alkylene glycols taught by Merianos are readily water soluble aliphatic diols but have little or no recognized antimicrobial activity, themselves, at use concentrations below about 10 weight percent in the finished preparation. Moreover, the Merianos liquid compositions require that the water soluble, dry blend of DMDMH and IPBC have a high weight ratio of DMDMH to IPBC ranging upwards from 100:1 to 2000:1.
Unfortunately, as the weight of DMDMH in the dry blend increases and the weight of the IPBC decreases, antifungal effectiveness decreases, as shown by tests and evaluations of the antifungal effectiveness of these dry blends reported by Merianos in Tables 21 and 22 of U.S. Pat. No. 5,428,050 and U.S. Pat. No. 5,496,842. Consequently, high levels of broad spectrum antimicrobial activity, especially against the yeast, Candida albicans (Ca), was not achieved by using such dry blends at the low usage concentrations that are desired for acceptable commercial practicality in personal care preparations. This presents a problem because the maximum amount of DMDMH containing antimicrobial compositions used in personal care preparations is limited in many countries by regulation.
Thus, the art needs a new and improved liquid composition for DMDMH and IPBC which, when admixed with an aqueous medium at a usage concentration preferably of no more than about one weight percent produces broad spectrum antimicrobial activity, and especially antifungal activity.
The present invention provides such a new and improved liquid composition.